When t/stat turns on with setting of 78deg inducer motor & blower kicks on then igintor kicks on then burner kicks on after little while burner turn-off then blower speed gets low , inducer motor still runs,green light blink with 3 times & hold again blink 3times,then inducer motor turns off, again doing the same cycle,temperature not rise more than 67deg,I am refrigeration tech,pls. give me some clue or hints to work on with,thanks
Sounds like its tripping a limit switch or if it has a flame rod .you may need to clean it. Possibly tripping the high limit due to dirty filter. usually has a diagnostic sheet on one of the panels that will tell you what is going on check the panel you see the light closest to.
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Induced fan motors on older units are wired through the high limit safety on the stack - in series. When the furnace calls for heat, the induced fan motor comes on and after a time the furnace will light.
Older units have a temp switch in the stack that rotates to bring on the burners and blower motor. . When there is a call for heat, the induced draft fan motor comes on and then the burners will light.
After the heat exchanger is warmed up the limit switch will bring the blower motor on. That's basically how it works - there are two circuits - one for the induced draft motor and the burners and the other for the blower and high limit.
New units have a plug on the board you just plug in.
Sounds like a faulty board. shut the power to the furnace off for a minute then turn it back on. Make a call for heat at the thermostat. The inducer should start and close contacts on a pressure switch . Once pressure switch closes the hot surface ignitor should glow red. Then the gas valve will open when the gas valve opens you should get fire till the stat is satisfied. If your concerned it is the jump out r to w on the board this will eliminate the stat. If you to reset the rollout switchs 3 timesyou're getting flame rollout and you either have a cracked heat exchanger or blockage in the exhaust piping or a bad inducer motor. Keep me posted with what you find!
First make sure that your thermostat is turned to heat and auto settings. Then turn up t-stat to where it should be calling for heat.If nothing happens then make sure you have power to heater, gas valve is turned on and blower compartment door is securely latched. If still nothing turn t-stat to fan on and the blower should come on and run until you shut it off. If it does this then you know that you have power to furnace and that the blower works.After you are sure that you have power then remove thermostat cover from base. If stat wires are connected to front of base then disconnect red and white wires and temporairly touch them together. This should send power to your furnace and start the ingnition cycle. If this works then replace thermostat. The sequence of events in the ignition cycle are t-stat calls for heat, induced draft motor comes on and runs for about 20 seconds,then ignitor comes on and lights pilot,then burner lights for 1-2 mins and then blower comes on. I would start at the t-stst and work my way through it. If I can be of any help please ask. Thank you
Does your unit have a induced draft motor? if so is it coming on when thermostat is calling for heat. If not I would replace it. Next I would check spark or hot surface ignitors. If induced draft motor is working but ignitors are not then replace them. If you get to this point and you don't get pilot or main burner I would replace the control board. As a last resort I would change gas valve. I hope this helps you and god luck. Thanks
When the furnace first comes on there is a induced draft motor that should come on first but that forces air up the exhaust or flue,not into supply air on ductwork. It is not unusual for cold air to be blown out when burner first turns blower motor on. This should last for a short period of time, no more than a min. or two. You can watch furnace cycle by removing top front cover, I should back up here and ask is this a gas or electric unit. If it is gas you should be able to watch burner flames for a short time before blower comes on. I really need more information so I can try to ascertain what is going on. Wish I could be more help. Thank you.
The inducer blower will put a vacuum on your pressure switch which in turn will tell the board to apply power to the ignitor. If you have a vent blockage, dirty air filter, plugged condensate line or any blockage of either vent or air intake, the furnace will lock-out and flash an error code on the circuit board. If after inspecting all the above for debris and found nothing, you can quickly jump the pressure switch after the inducer starts to see if the ignitor glows. You could also have a bad ignitor. Yes the lock-out is normal. Looks like you discovered the cause on your own, order a new switch.
Is the blower wheel turning? Did you by chance have to remove the motor from the blower wheel to work on it? If you did, did you put the blower wheel back on in the correct direction of air flow? Also, did you put the correct capacitor back on the unit so it can get up to the required rpm's? These are things that you will need to check for. If the motor is running and the blower wheel isn't and the wheel is tight on the shaft, then you will have to replace the motor. The brushes may be bad on the unit and it's not turning the shaft. Hope these ideas help.
You are referring to the inducer motor that is kicking on and off. It is probably a limit switch that might be triggering it to go off and on over and over. It could possibly be the board but I highly doubt it since the ac works just fine. It can also be a short in the wiring going to the inducer motor as well or the inducer motor is going bad. Without checking it out myself with a voltage meter, it's hard to pinpoint exactly what is causing the issue but I highly doubt it is the main board. Get a second opinion.
be sure the fan setting on the stat is set for auto, not on. in this mode the fan should only run when there is a call for cool or heat.if the fan continues to run check at the control board to see if you are getting 24 volts low voltage between green and common. if you are then the stat is bad. if youaren't then your electric control board is possibly bad. a lot of gas furnaces fall into a failsafe mode when a sensor or function fails and the blowers stay on 24 7. you may well have several problems from what you are saying. if you turn everthing off and start a new cycle for heat the first thing that should fire up is the induced draft motor , then the ignotor, then the gas valve. you can check each item with a meter , generally 120 volts to the induced draft motor, then 120 volts to the ignitior, the 24 volts to the gas valve. then ignition and 120 volts to the motor. most furnaces have a heat terminal and a cool terminal on the board. common to heat should get 120 volts on a call for heat after the sequence of operationb has taken place. 120 volts should be sent to cool terminal on a call for cool. a continueous blower is a sign of a failed safety. perhaps the motor failed and the safety opened and the motor was replaced but the safety never reset?. look at all the little micro temp sensors around the burner. they are like little breakers and need to be pushed in to reset . usually like a little stem that pops out from a metal or plastic dic. some are size of a quarter, some the size of a dime.
most forced draft fans are powered by 120 volts . close to the fan is usually a plug that unsnaps. create a call for heat after turning off to clear safetys and see if your getting 120 to fan on initial call for heat. if you are then fan draft motor is bad, usually sold as an entire assembly replace exact as it came out. sequence of operation is..... stat calls for heat via common and white wire to furnace , 24 volts. ......board sences call and sends 120 volts to forced draft ........ motor runs and creates pressure on proofing switch,....... switch closes 24 to board and tells it draft fan is on......... board then energizes ignitor,....... after ignitior glows gas valve is opened and burner lights ........ either ignitor or seperate sensor rod tells board the burner lit........ and a few minutes later the fan comes on and hot air is blown out. if a step is missed or doesn't proof the furnace either trys up to three times to light or locks out. turning off power usually resets safetys and it will resume attempts to lite normally.